The interconversion of δ2H values of collagen between thermal conversion reactor configurations

• Published in: Rapid communications in mass spectrometry 2019-04, Vol.33 (7), p.678-682
• Main Authors: Reynard, Linda M., Ryan, Saskia E., Tuross, Noreen
• Format: Article
• Language: English
• Subjects: Carbon; Chromium; Collagen; Configurations; Conversion; Glassy carbon; Historic sites; Isotope ratios; Nitrogen
• ISSN: 0951-4198; 1097-0231
• DOI: 10.1002/rcm.8396

Rationale Different thermal conversion reactor packings result in distinct δ2H values in nitrogen‐containing materials, such as bone collagen. An older ‘traditional’ glassy carbon packing method causes incomplete conversion of N‐containing samples into H2 gas, resulting in altered δ2H values compared with the complete conversion of hydrogen obtained with a chromium‐packed reactor. Given that δ2H values from collagen are gaining importance in palaeoecological and archaeological studies, a determination of the relationship between δ2H values produced with a glassy‐carbon‐packed and a chromium‐packed reactor is needed. Methods We obtained δ2H values (normalized on the VSMOW‐SLAP scale) from both glassy‐carbon‐packed (GP) and chromium‐packed (Cr) reactor configurations from bone collagen (n = 231) from a variety of archaeological sites, using a High‐Temperature Conversion Elemental Analyzer (TC/EA) coupled to a Delta Plus XP isotope ratio mass spectrometer. Results δ2H values from both methods are linearly correlated (r2 = 0.934) and yield the following interconversion equation, δ2H(Cr) = 1.054 δ2H(GP) + 11.6‰ (95% conf. slope 1.020–1.090, intercept 10.6–12.6), and a mean difference of δ2H(Cr) – δ2H(GP) = 10.1‰ (1 sd 5.2, 1 se 0.3, n = 231). Conclusions We recommend adopting this interconversion between δ2H values produced with a glassy‐carbon‐packed and chromium‐packed reactor for bone collagen only, with appropriate propagation of uncertainty.